There are many types of electrical devices operating on line power whose housing must be opened at times for servicing and replacing parts. There is always a concern that these devices will be opened without first removing the power by unplugging the power cord or tripping the circuit breaker. Television sets for example having removable back covers incorporate plugs in the back covers. The plug in the cover is designed to mate with a plug in the chassis when the cover is assembled to the set. In this way, power automatically disconnects when the cover is removed. In such a device, power is supplied to the back cover by the power cord but no electrical component is present in the back cover which uses this power.
There are other devices though whose housings are formed of two halves, where it is a design convenience to supply line power directly to the half which has a component operated by line power. As one example, some humidifiers designed for permanent attachment in ductwork have in a removable housing cover, a fan which operates on line power. A base with which the cover mates is permanently installed in the duct. A transformer in the cover steps down line voltage to 24 v. to operate a solenoid valve in the base for regulating water flow to the humidifier, and for connection to the humidistat. The humidistat completes the 24 v. circuit, powering the solenoid and operating a relay which controls fan power. It is necessary to regularly replace a pad onto which the water is dispensed while the humidifier is operating. Replacing this pad requires the humidifier housing to be opened. This operation is safer if the fan is disabled while the housing is open.
U.S. Pat. No. 5,252,260, which issued to Schuman on Oct. 12, 1993, describes a humidifier including an internal connector plug having first and second halves which are integrated into the humidifier's cover and base respectively. When the cover is mated to the base, the two connector plug halves are mated automatically to form the electrical connections which allow operation of the humidifier. I hereby incorporate by reference the '260 patent into this application.